1. Field of the Disclosure
The present invention relates to a touch panel integrated display device which can reduce an entire thickness and weight and which can prevent display quality deterioration.
2. Discussion of the Related Art
With serious start of an information age, a display field which presents electrical information signals visually has been developed drastically. A variety of flat display devices having compact-sizes, lightweights and low power consumption have been developed and replaced conventional cathode ray tubes (CRT).
Such a flat display device includes a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), an electro luminescence display device (ELD) and an electro-wetting display (EWD). The flat display device has to have a display panel configured to display images, with a pair of insulation substrates bonded with each other in opposite, having a light-emitting material layer or polarized material layer disposed there between.
A liquid crystal display device is a device which can display images by using a light transmittance of liquid crystal which can be adjusted according to an electric field. The liquid crystal display device has advantages of a small-sized, slim appearance and low power consumption. Because of that, the liquid crystal display devices have been applied to notebooks, office automation devices and audio/video devices broadly.
Typically, each of personal computers, portable communication devices and the other personal information processing devices forms an interface with a user via an input device including a keyboard, mouse, digitizer, etc. Recently, it is difficult for the input device such as a keyboard and a mouse to enhance a degree of completion of a product, as development of mobile communication equipments have been expanded in recent. Because of that, input devices with a high portability which can be used more simply have been developed continuously and a touch panel allowing information to be input via a direct touch of a screen, using his or her finger or pen has been proposed.
The touch panel enables letters to be input simply with fewer malfunctions, if auxiliary letter input devices are not provided and it is easy to carry with and for the user to recognize a user manual. Because of those advantages, the touch panels have been applied to a variety of information processing devices recently. Especially, when the user selects an icon or keyboard displayed on a screen, a corresponding icon or keyboard provided in the touch panel may be selected to input information. To enable that, a flat display device including such the touch panel has been applied to a portable information processing device such as a personal computer and a mobile phone often. A touch panel attached liquid crystal display device which includes a touch panel attached to a liquid crystal panel provided therein is proposed as one of flat display devices including the touch panels.
FIG. 1 is a diagram illustrating a conventional touch panel attached liquid crystal display device.
As shown in FIG. 1, the conventional touch panel attached liquid crystal display device includes a liquid crystal panel 10 configured to display images by adjusting a light transmittance of each pixel using a direction of liquid crystal cells, a touch panel 20 configured to sense a touch, and a adhesive layer 30 configured to bond the liquid crystal panel 10 with the touch panel 20.
The liquid crystal panel 10 includes a pair of substrates oppositely bonded with each other, with a liquid crystal layer located there between, a transistor array provided on either of the two substrates to define each of pixel regions corresponding to each of the pixels and to control brightness of each pixel, and a color filter array provided on either of the substrates to transmit various color lights corresponding to the pixels, respectively. First and second polarization layers 11 and 12 are formed on top and bottom surfaces of the liquid crystal panel 10, respectively. The first polarization layer 11 polarizes a light incident to the liquid crystal panel 10 and the second polarization layer 12 polarizes lights emitted from the liquid crystal panel 10.
The touch panel 20 includes a transparent substrate 21 provided as waveguide to allow a light transmitted with less loss, light sources 22 adjacent to the transparent substrate 21 to project a light into the transparent substrate 21, a reflective plate 23 adjacent to the transparent substrate 21, opposite to the light sources 22, to reflect the light transmitting the inside of the transparent substrate 21 and to supply lights traveling straight in parallel to a top surface of the transparent substrate 21, and a sensor 24 formed on a peripheral area of the top surface of the transparent substrate 21, opposite to the reflective plate 23, to collect the lights passing along the top surface of the transparent substrate 21. Such the touch panel 20 detects a coordinate corresponding to the sensor 24 not receiving the light, by using that the light passing along the top surface of the transparent substrate 21 is reflected by a touch generated at a predetermined area of the transparent substrate 21, only to detect a coordinate of a touch point.
According to the prior art, the light emitted from the light source 22 can reach the sensor 24 only via the process of transmitting the inside of transparent substrate, the process of being reflected by the reflective plate and the process of the straight-moving over the top surface of the transparent substrate 21. That is, quite a large percentage of the radiation intensity of the lights emitted from the light source 22 may be decreased by a long light passage to the sensor 24. Because of that, the light collected in the sensor 24 has a relatively small quantity of the radiation intensity only to have a high possibility of failing to be effectively recognized by a control unit (not shown). As a result, it is limited to improve a touch sensing sensitivity of the touch panel.
Furthermore, according to the conventional touch panel attached liquid crystal display device, the liquid crystal panel 10 including the pair of the substrates and the touch panel 20 including the auxiliary transparent substrate 21 are provided independently. After that, the touch panel 20 is adhered to the liquid crystal panel 10 by the adhesive layer 30. The pair of the substrates of the liquid crystal panel 10 and the transparent substrate 21 of the touch panel 20 are provided independently. Because of that, it is limited to reduce the entire weight and thickness of the conventional touch panel integrated display device. In addition, the bonding process between the liquid crystal panel 10 and the touch panel 20 has to be performed. Because of that, a manufacturing process can be complex and it can be difficult to improve the yield.
A still further, the light emitted from the liquid crystal panel 10 to display an image (hereinafter, “display light”) has to pass the adhesive layer 30 and the touch panel 20, to be emitted outside. Because of that, a transmittance of the display light happens to be lowered, and thus the image quality of the liquid crystal panel 10 might deteriorate disadvantageously.